1. Field
The present embodiments relate to toner for developing an electrostatic image and a method of preparing the same.
2. Description of the Related Art
Methods of preparing toner particles suitable for an electrophotographic process and an electrostatic image recording process may be largely classified into a pulverization process and a polymerization process.
Conventionally, toners used in an image-forming apparatus are mostly obtained by a pulverization process. However, in the pulverization process, it is difficult to precisely control the particle size, geometric size distribution, and the structure of toner, and thus, it is difficult to separately control the major characteristics of toner, such as charging characteristics, fixability, flowability, and storage characteristics.
Recently, the use of polymerization toner has increased due to a simpler manufacturing process, which does not require sorting particles and due also to the ease of controlling the size of the particles. When toner is prepared through the polymerization process, polymerization toner having a desired particle size and particle size distribution can be obtained without pulverizing or sorting. Since toner prepared according to the polymerization process has a smaller particle size and narrower geometric size distribution than toner prepared according to the pulverization process, an image-forming apparatus using the toner prepared according to the polymerization process has high charging and transferring efficiency, excellent dot and line reproducibility, low toner consumption, and high image quality. Recently, interest in the environment has increased when manufacturing toner according to the polymerization process. Accordingly, there is continuous interest in increasing durability of a system element and low-temperature fixation, which is advantageous in reducing energy consumption, is drawing attention.
U.S. Pat. No. 6,617,091 discloses a toner particle, wherein a resin layer (shell) is formed on a surface of a colorant particle (core particle) containing a resin and a colorant, to provide polymerization toner that does not change image concentration, fog an image, or change a color of the image resulting from a change of charging and developing properties, even when the amount of colorant existing on a particle surface is small and the polymerization toner is provided for a long time under high humidity. According to such polymerization toner, the uniformity of charging may be somewhat increased by suppressing exposure of a surface of a pigment. However, for example, when the polymerization toner contains lots of wax, high-temperature storage characteristics and flowability of the polymerization toner may deteriorate due to a plasticizing effect according to compatibility between a low molecular portion of the wax and the resin. A method of encapsulating a surface of a binder resin having a low glass transition temperature with a binder resin having a somewhat high glass transition temperature has also been suggested for low-temperature fixation. According to such a method, the low-temperature fixation may be achieved but high-temperature storage characteristics may not be satisfactory.